If several receivers hear the same signal at slightly different moments, you can work out where the transmitter is — just as you estimate how far away a storm is from the gap between lightning and thunder.
In practiceIn Ukraine both sides locate drone pilots and radio posts by their transmissions and then strike them with artillery or drones. Operators therefore transmit briefly, use directional antennas and move often.
Before you jam or deceive, you want to know where the transmitter is. That starts with direction finding (DF): determining the direction from the signal. With several receivers at known positions you can go further and geolocate the transmitter. Two techniques that are often used together:
- TDOA (Time Difference Of Arrival): several receivers measure the difference in time at which the same signal arrives. Each time difference places the transmitter on a curve (a hyperbola); where the curves of several pairs intersect, that is where the transmitter is.
- FDOA (Frequency Difference Of Arrival): moving receivers (aircraft, satellites) measure small frequency differences caused by the Doppler effect. This adds extra curves and sharpens the position, especially from the air or space.
Finally, communications EW also includes deception: imitative deception (injecting false messages that look genuine — touching on CEMA, CEMA: cyber & EW) and manipulative deception (manipulating your own traffic pattern to mislead the enemy's COMINT).
This chapter completes the EW picture: ES (EW: Electronic Support Measures) is not only radar ELINT but also COMINT with DF and geolocation; EA (Electronic Counter Measures) is not only radar jamming but also COMJAM. The key lesson: effective COMJAM is rarely brute force — it is the right technique, at the right place in the protocol, from the right geometry, based on good COMINT. And the flip side: COMJAM also disrupts your own nets (fratricide, Doctrine & EMSO) — hence the JRFL and strict EMCON discipline.